Welding flux for joining copper-nickel alloys

ABSTRACT

A FLUX AND FLUX COVERED WELDING ELECTRODE FOR WELDING COPPER-NICKEL ALLOYS, PARTICULARLY THOSE CONTAINING CHROMIUM. IF CHROMIUM IS ABSENT FROM FLUX, WELD CRACKING LIKELY. IN ADDITION TO CHROMIUM, FLUX CONTAINS CALCIUM CARBONZTE, CRYOLITE, TITANIA, SILICON AND TITANIUM. USE OF MANGANESE CARBONATE AND BENTONITE BENEFICIAL.

United States Patent 3,560,273 WELDING FLUX FOR JOINING COPPER-NICKELALLOYS Walter A. Petersen, Ridgewood, N..I., assignor to TheInternational Nickel Company, Inc., New York, N.Y. No Drawing. FiledJuly 1, 1968, Ser. No. 741,286

Int. Cl. B23k 35/36 US. Cl. 14824 5 Claims ABSTRACT OF THE DISCLOSURE Aflux and flux covered welding electrode for welding copper-nickelalloys, particularly those containing chromium. If chromium is absentfrom flux, weld cracking likely. In addition to chromium, flux containscalcium carbonate, cryolite, titania, silicon and titanium. Use ofmanganese carbonate and bentonite beneficial.

As set forth in my application Ser. No. 707,967, filed Feb. 26, 1968 andcopending herewith, the introduction of special amounts of chromium intootherwise age-old, conventional copper-nickel alloys (cupronickels) ofthe 70/30 type brought about a remarkable improvement in mechanicalcharacteristics, notably tensile strength. However, as further setforth, an attendant weldability problem arose, a problem which, sufficeto say, obscured the commercial potential and development of these newhigh strength materials.

In any event, a bare metal filler composition (described in saidapplication Ser. No. 707,967) was devised which, in retrospect, must besaid to have but partially eliminated the difliculty. For, as will beillustrated herein, a situation somewhat unexpected came about. When theidentical bare filler metal composition which had given suchsatisfactory results theretofore was used in conjunction with a fluxcoating, i.e., a flux covered electrode, failure reappeared. This seemedparticularly anomolous since the flux itself was one which had performedsuccessfully in welding of the standard, conventional 70/30cupronickels.

There is little question that the use of flux covered electrodes hasbeen replaced in many applications by automatic (and semiautomatic, forthat matter) inert gas shielded-arc-welding, as exemplified by both theTIG (gas shielded tungsten-arc) and MIG (gas metal arc) techniques.Nonetheless, there are industrial and commercial applications in whichsuch techniques have extremely limited, if any, utility. And thusrecourse to covered electrodes or the like is unavoidable, due regardbeing given to present welding technology.

The use of covered electrodes can be understood by reference to theprimary area of application of the cupronickels, to wit, marine service.Consider, for example, the shipboard installation (or repair) of highpressure piping systems common to any number of naval vessels. Whetherit be installation or repair, the weld work in respect of such systemsis often performed under the most limited and cramped conditions, otherpiping and components being in close proximity. Actually, welders arenot infrequently forced to use mirrors simply to see the area to bewelded. If for no other reason, the sheer bulk of inert gas shielded-arcwelding equipment would restrict proper manipulation thereof under suchconditions to the point of total futility. It might also be added thatcovered electrodes are not without other advantages, including lowerinitial cost of equipment, simplicity with which a job can be set up(amenability to short runs), and usefulness in field weldingparticularly maneuverability.

The theory which might possibly explain the metal- 'ice lurgicalphenomenon involved is not completely understood. As was the case withthe bare metal filler material, chromium seemingly plays a mostimportant role, but, however, in a most different fashion. If thisconstituent-the element responsible for the striking increase instrength in the first place-is found in the core material (i.e., corewire) but not in the flux undesirable cracking can too easily result.But if contained in the fiux in a proper amount, weld cracking can beavoided, particularly if other prerequisites herein described are met.

It has now been discovered that sound, high strength substantiallycrack-free, copper-nickel-chrornium welds (and overlays), welds whichare also substantially nonporous, ductile, tough and corrosionresistant, can be produced particularly in respect of applications inwhich bare filler metal compositions per se would be unsuitable orimpractical. As described in greater detail infra, this requires aspecial combination of flux and core wire. The covered electrode inaccordance herewith is further characterized in that it is anall-position welding element, offering ease of operation in the fiat,vertical, and overhead welding position. In addition, slag that formsduring welding is easily removable by light chipping-it has beenobserved to break away from deposits by itself. Usually r only lightwire brushing is required between weld passes.

Of further importance, weld deposits are readily obtained having tensilestrengths comparable to the welded copper-nickel-chromium base metal.Moreover, post weld heat treating is not required, and this is mostsignificant when due consideration is given to the conditions underwhich such electrodes are likely to be used, i.e., where space is at apremium. If post weld heat treating were required, the utility of theflux covered electrode would be greatly curtailed.

It is an object of the invention to provide a new and improvedchromium-containing flux composition suitable for use in weldingcopper-nickel alloys, particularly high strength, chromium-containingcopper-nickel alloys.

The invention also contemplates providing a flux covered electrode, theflux and core material coacting to produce sound, substantiallycrack-free and nonporous weld deposits in respect of copper-nickel alloybase members.

Another object of the invention is to provide new and improved weldedstructures in which the weld deposit and at least one other member is ofa high strength, chromium-containing cupronickel.

Other objects and advantages will become apparent from the followingdescription.

Generally speaking and in accordance herewith, the present inventioncontemplates using a special flux covered electrode to weldcopper-nickel alloy base members containing about 24% to 38% nickel, andparticularly with at least one member containing about 2.4% to 3.8%chromium (as described in the US. patent application of Frank A. Badiaand Gary N. Kirby, Ser. No. 708,793 filed on Feb. 28, 1968). Otherconstituents which can be present in one or more of the members are asfollows: up to 2.5%, e.g., up to 1%, iron; up to 2.5% cobalt, with thesum of the chromium, iron and cobalt not exceeding about 5%; up to 6%zinc; up to 3% manganese; up to 0.8% zirconium; up to 0.5% each ofsilicon, titanium, aluminum, columbium and beryllium; up to 0.1% carbon;up to 0.1% magnesium; and the balance essentially copper.

In terms of composition, the flux of the subject invention is comprisedof about 10% to 40% calcium carbonate, about 5% to 40% cryolite, up to30% manganese carbonate, about 10% to 35% titania, about 7% to not morethan 13% chromium, about 0.6% to 1.7% silicon, about 0.5% to 1.6%titanium, and up to about 5%, e.g., 2% to 5%, bentonite. Usually a waterdispersible binder such as sodium silicate, potassium silicate, and thelike is used to promote the formation of a relatively hard and durablecoating subsequent to drying as by baking.

Calcium carbonate primarily serves the function of providing therelatively inert shielding gas carbon dioxide which shields the depositfrom the atmosphere. It also assists in the cleansing of the weld metaland while it can be present in an amount from to 40%, a range of 16% to24% is deemed most beneficial for ease of operation, good shieldingeffect and minimization of the tendency for difficultly removablepowdery slag to form. In respect of cryolite, the principal role thereofis its action as a cleaning agent. It promotes the removal of oxidesfrom the weld pool and also contributes to imparting weld soundness. Bymaintaining the content thereof from 16% to 24%, difiiculty thatotherwise might be encountered with regard to subsequent slag removal isgreatly lessened.

With regard to manganese carbonate, it chemically breaks down during thewelding process into, inter alia, manganese and carbon dioxide, thelatter performing, as indicated herein, as a shielding gas. It is ofconsiderable benefit with respect to ease of slag removal and thus it isadvantageous that the flux contain this constituent, particularly withinthe range of 16% to 24%. The relatively high amount of manganeseintroduced into the weld deposit does not exert a detrimental influence.Titania serves as an arc stabilizer and provides a spray-type transfer.As a result, a welder is permitted greater freedom of movement in tightor close quarters than otherwise might be the case. With too small aquantity of titania, an obnoxious powdery slag is likely to form; on theother hand, if present to the excess, weld cracking is apt to follow.From 16% to 24% titania gives highly satisfactory results.

As referred to herein, if chromium is found in the core material but notin the flux, weld cracking is likely. Chromium, the principalstrengthening element, is transferred across the are from the coating,complete alloying taking place during the fusion process. The fluxchromium powder remains the principal source of chromium ultimatelyfound in the weld deposit, notwithstanding the percentage thereof in thebase metal (member) since but a small amount of the latter is obtainedin the deposit via dilution. This is particularly true in heavy sectionwelds. Taking this low dilution factor into account and with the view ofobtaining deposits of high strength, at least 10% chromium should be inthe flux in the welding of sections 1 inch in thickness or more and atleast 9% chromium for, say, /2 inch thick welds. This enables obtainingweld deposits having a yield strength on the order of about 50,000 psi.(and above), a strength level comparable to that characteristic of thechromium-containing cuproniekels under consideration. Yield strengths of40,000 psi. can be achieved consistently with down to 7% chromium in theflux, though at least 8% is preferred.

Simply using high chromium levels, however, is not a complete panaceaunto itself since, as will be shown herein, excess chromium has beenfound to promote or is causative of cracking in heavy section welds.Thus in 4 welding heavy sections of one inch or greater, it is ofconsiderable benefit to control the chromium content of the flux suchthat it does not exceed about 12%.

The function of silicon is of particular importance. It increases thefluidity of the slag and weld metal and also acts as a deoxidizer. Moreimportantly perhaps and particularly in heavy section welds, i.e., aboutone inch or greater, if an insufiicient amount is present, weld crackingwill ensue. But by the same token, however, and under the sameconditions with all other factors remaining equal, an excessive amountof silicon can bring about cracking as will be shown herein.Accordingly, while necessary to prevent cracking, particularly in heavysections and particularly at chromium levels at, say, 11% or 12%, itmust also be controlled to inhibit cracking. While a silicon content of0.8% to 1.4% is quite advantageous, for Welding sections of about oneinch or more in thickness, the respective amounts of chromium andsilicon should be correlated as set forth in Table I.

TABLE I Percent chromium: Percent silicon 9 0.75-1.3 10 O.91.25 110.951.2 12 11.2

For values intermediate those given in Table I, interpolation should beused. In making the silicon addition, it is preferred to use anickel-silicon alloy containing 28% silicon, a product commerciallyavailable. A 4% addition of this alloy has consistently given excellentresults. The use of this master alloy introduces some nickel into theflux but this is, of course, quite unobjectionable since nickelconstitutes a high proportion of the core material as well as the basemembers welded.

In respect of titanium, its primary flux role is as a deoxidant. Amountssignificantly below about 0.5% and above 1.6% have resulted in crackedwelds in X-weld tests. A range of 1% to 1.5% is most advantageous. As isthe case with silicon, it is preferred to add the titanium via acommercially produced nickel-titanium master alloy (26% titanium), theuse of 5% of this master alloy having consistently proven to beextremely efiective.

For the purpose of giving those skilled in the art a betterunderstanding of the invention, the following examples and data aregiven:

A significant number of fiux compositions were formulated and used inconducting a series of X-weld tests. The compositions of the variousfluxes are given and identified in Table II. It should be mentioned thatabout 15% sodium silicate was added in each instance as a binder.Moreover, since the fluxes were extruded on to the core wires, the fluxcompositions contained 3% bentonite which performs extremely well inenhancing extrudability. Unless otherwise specified, the composition ofbase metal members was as follows: 29.3% nickel, 2.95% chromium, 0.07%silicon, 0.71% manganese, 0.08% titanium, 0.79% iron, 0.17% zirconium,the balance being copper and incidental impurities.

n.a.=none added.

Silicon added as nickeksilicon (28% Titanium added as nickel-titaniumExcept Where silicon and titanium were nickel from the master alloyadditions.

silicon) master alloy. (26% titanium) master alloy.

not added, balance of fluxes was essentially EXAMPLE I Chromium-freeflux l-A of Table II was extruded (approximately 0.22 inch outsidediameter) on to a %2 inch diameter cupronickel core wire containingabout 6 EXAMPLE 1v Using a chromium-free core wire but achromiumcontaining flux, flux 1-C, the X-weld test was once againcarried out as described in Example I. The core wire 30.1% nickel, 2.5%chromium, 0.22% silicon, 0.84% 5 contained, in addition to copper, 31.8%nickel, 0.10% manganese, 0.04% titanium, less than 0.03% zirconiumsilicon, 0.69% manganese, 0.6% iron and 0.26% titaniand the balanceessentially copper. This core Wire comum. Upon examination of thetransverse slices, no cracks position had been previously successfullyemployed for were observed. The weld was substantially nonporous andtungsten-arc welding. After drying, the covered electrode ductile.Analysis of the deposit showed that it contained was used in making anX-weld crack test to stimulate the 10 29.8% nickel, 2.20% chromium,1.72% manganese, severe conditions encountered in welding heavysections. 0.21% silicon, 0.05% titanium, less than 0.02% zirconi- (Adescription of this procedure and illustrations thereof um, 0.77% iron,balance copper and impurities.

are found in The Welding Journal, vol. 24, November EXAMPLES V, VI ANDVII In conducting the test, two one-inch square by three- Uslflgchromlqrp-wfltalnlng fluxes LE and inches long bars were clamped withtheir edges together three; addlilonal tests fi i l out the S to form anX joint. Eighteen passes were made, nine on manner PP I but a Wlre ofthe either side, alternating from side to side, using one halfcomposltlon glven 111 EXamPIe In Instance were of an electrode per passUpon completion, the 1d weld cracks detected. Together w1th Example IV,these formed was cut into transverse slices with foulfaces th testsdemonstrate that excellent welds can be obtalned ing ground, polished,etched and then examined for deover a Chromlum (flux) range of 9% tofects. 1 i & EXAMPLE VIII y i e r i l mhthefileat a s 2; As indicatedabove herein, in the welding of thick secg i a r if g l g a i lf g' i iitions, silicon plays a vital role. As the chromium content f 1 b E V iof the flux is increased above about 8% or 9%, the silif ge g a d'eemcon must also be increased as reflected in Table I. To 3: 2 g g us gmlum' me X as 6 illustrate this point, a substantial number of flux com-EXAMPLE H positions are given in Table III. An indication is also setforth as to whether cracking was experienced and if so,

Again using a chromium-free flux, flux 1-B, and the thellengflziof t i ii same mode of operation as set forth in Example I, a cOre 3 i e d craiki agam were wire containing 30.0% nickel, 2.70% chromium, 0.32% Came outt e Set Orth .XamPle base silicon, 0.68% manganese, 0.04% titanium,0.74% iron, plate b f of p dlfiterent composmons were used 0.04%zirconium, the balance being essentially copper, the composmons being asfollows: was coated by extrusion. The transverse slices cut from BPMA!the weld exhibited 4.25 cracks per section (17 in all), the Ni, 3.15%Cr, 0.66% Mn, 0.15% S1, less length of the longest crack being about %ginch. than (105% T1, 073% 009% the balance Cu and impurities. EXAMPLEIII BPM-Z: l 29.3% Ni, 2.95% Cr, 0.71% Mn, less than 0.07%

Reducing the chromium content of the core w1re to the Si, 008% Ti, 0.79%Fe, 0.17% Zr, the balance vlrtual mmimum that would be present in achromlum- Cu and impurities. containing cupronickel base member ofminimum strength BPM-3:

did not prove to be of significant benefit. Thus, using Ilux 28.8% Ni,2.95% Cr, 0.77% Mn, 0.06% Si, 0.08% 1B and a core wire containing but2.35% chromium Ti, 0,79% Fe, 0,17% Zr, th b lan C d imtogether w1th30.2% nlckel, 1.04% manganese, 0.32% purities. silicon, 0.06% titanium,0.07% zirconium, balance essen- RPM-4; tially copper, a total of aboutfour cracks per section were r 28.8% Ni, 2.20% Cr, 0.67% Mn, 0.05 Siobserved after conducting the X-weld test in the manner (nominal), 0.10%Ti (nominal), 1.0% Fe, 0.020% of Example I. Zr (nominal), the balance Cuand impurities.

TABLE III Length Fluid CaCO Na AlFa, MnCO T102, 0 Si, T1, 011 Base nu liilie r of 89551? percent percent percent percent percent percentpercent percent plate cracks incli 22 21 20 2 22 21 20 2 3 1.2 5 Balance18 m 21 20 20 20 0 0. 20 20 20 20 0 0.84 20 20 20 20 0 0.84 21 20 19 190 1.12 1.3 20 20 20 10 0 1.12 1.3 20 20 20 19 9 1.12 1.3 20 20 10 10 01.4 1.3 20 20 10 10 9 1.4 1.3 21 20 19 19 0 1.4 1. 04 21 20 20 20 9 1.40. 52 21 10 10 18 0 1.4 1. 50 21 18 18 18 0 1.4 2.08 20 20 20 10 10 0.841.3 20 20 19 10 10 1.12 1.3 20 20 19 19 10 1.12 1.3 20 20 19 10 10 1.121.3 21 10 10 1s 10 1.4 1.3 20 10 19 19 12 0.84 1.3 10 10 10 10 12 1.121.3 21 18 18 18 12 1.4 1.3

19 19 18 18 14 1.12 1.3 t 20 18 1s 17 14 1.4 1.3 .do BPM-l 1 15%SOClllIn silicate added as binder and water as needed. Also 3% bentoniteadde Ni Ti master alloys.

. Silicon and titanium added as Ni-Si and The same core wire compositionwas used in all tests, the composition being the same as that given inconnection with Example IV except one test in which flux lP was used. Inthis particular instance, the core wire (chromium-free) contained 31.8%nickel, 0.32% manganese, 0.05% silicon, 0.03% titanum, the balance beingcopper and impurities.

In the tests using fluxes lG and 1H either silicon or titanium wasomitted from the flux and as a consequence the results were quite poor.The experiments involving fluxes 1-I through l-T should be consideredtogether. In each of this series of tests the chromium was heldconstant, to wit, at the level of 9%. Flux lI contained an insufllcientamount of siliconthus cracking was experienced. When this silicon level(0.56%) was raised to 0.84% or 1.12% as shown by fluxes 1] through lN,there was a complete absence of cracking. Raising the silicon content to1.4%, however, resulted in cracking as particularly evident from fluxesl-O and l-P. This confirms what has been previously stated hereinwhilesilicon is needed to prevent cracking it can, unless controlled, bepresent in amounts sufliciently high to bring about cracking. Thisadverse effect was not remedied by changing the percentage of titaniumor other flux constituents as is reflected by fluxes lQ through l-T.

The pattern of behavior experienced with the fluxes containing 9%chromium was also encountered with other groups of fluxes in which thechromium content was maintained constant. Thus with regard to fluxes lUthrough l-Y the level of chromium Was held at 10% and the data indicatethe presence or absence of cracks was dictated by the amount of siliconpresent. The same can be seen for fluxes lZ, AA and BB in which theamount of chromium was controlled at 12%. The X-weld crack tests usingfluxes CC and DD are included for the purpose of demonstrating that at achromium level of 14%, cracking was rather severe regardless of the factthat an amount of silicon (1.12%) was used which had given excellentresults in respect of the tests using fluxes lL, lM, l-N, lV, lW and lX.And raising the silicon content served but to aggravate the situation.Accordingly, for consistently achieving highly satisfactory results,

8 In addition to the base plate identified above as BPM-4,

other base plate member compositions were employed as follows.

29.1% Ni, 3.75% Cr, 0.43% Mn, 0.05% Si (nomi nal), 0.10% Ti, 0.82% Fe,0.20% Zr (nominal), balance Cu and impurities.

BPM-6:

29.1% Ni, 3.0% Cr, 0.76% Mn, 0.09% Si, 0.04% Ti, 0.51% Fe, 0.03% Zr,balance Cu and impurities.

29.6% Ni, 2.92% Cr, 0.61% Mn, 0.05% Si, 0.07% Ti, 0.17% Fe, 0.13% Zr,balance Cu and impurities.

The compositions of the various core wires employed are set forth below:

CW-l:

31.8% Ni, 0.69% Mn, 0.10% Si, 0.26% Ti, 0.60% Fe, balance Cu andimpurities (same as fluxes in Table III, except flux 1-P). CW-Z:

32.9% Ni, 0.94% Mn, 0.09% Si, 0.25% Ti, 0.36%

Fe, balance Cu and impurities. CW3:

29.8% Ni, 72% M11, 0.09% Si, 0.27% Ti, 0.53%

Fe, 0.02% C, balance Cu and impurities.

Welds were formed from the flat, vertical and overhead positions. (Foroverhead welding, the assembly was inverted and bolted to a fixtureabout 6 feet above the floor to enable the welding operation to becarried out.) The amperage used depended upon the core wire diameterapproximately amps being used for wires inch in diameter, 80 amps forwires /8 inch in diameter and about 100 amps for wires inch in diameter.The joints were radiographically inspected using a 300 kilovolt ampere(k.v.a.) X-ray unit. The results of the radiographic inspection testsare reported in Table IV together with flux composition, base plate andcore wire identification and Whether the butt-weld was in the flat,vertical or overhead position.

TABLE IV Cr, Si, Ti, C8003, NElsAlFfl, MnCO3, T102. perperper- On, BaseCore Radiographic percent percent percent percent cent cent cent percentplate wire Position inspection 21 20 20 20 7 1.12 1.3 Balance... BPM-7CW-l Flat N0 cracks. 20 20 20 20 9 0. 84 1. 3 do BPM-7 CW-l do- Nocracks; nonporous. 2O 20 20 20 9 0.84 1.3 d BPM-7 CW-1 do Do. 20 20 1020 9 1. 12 1. 3 --d BPM-4 CW-l Ove DO. 20 20 10 20 9 1. l2 1. 3 d BPM -6D0. 20 20 19 20 0 1.12 1.3 do BPM -6 Do. 21 19 10 19 9 1. 4 1.3 doBPM-fi No cracks; 3 pores. 21 19 1t) 1!) 9 1. 4 1. 3 do BPM-4 CW-1 Flat.No cracks; nonporous. 21 10 1t) 10 9 1. 4 1, 3 do BPM-4 CW2 Ve1'tica1 N0cracks; 6 pores. 2O 20 10 19 10 1.12 1. 3 do BPM 7 CW-l Flat- No cracks:nonporous. 20 20 19 19 1O 1. 12 1. 3 .d0 BPM-7 CW2 Overhead No cracks; 4pores. 20 20 19 19 10 1. 12 1. 3 do BPM-4 CW-3 VerticaL No cracks; 6pores. 20 1o 19 10 11 1.12 1.3 do BPM -7 CW-2 Flat No cracks; nonporous.

1 Joint thickness 1 inch rather than inch. 3% N i-Ti master alloys used.

2 Very slight porosity.

bentonite and 15% the percentage of chromium in the flux should notexceed about 13%.

EXAMPLE IX In addition to the X-weld tests described above, a number ofbutt-welds was also prepared and tested. Generally speaking, plates /2inch thick, 2% inches in width and 5 to 6 inches in length were used,the plates being beveled along the 5 inch edge at an angle of 30. Thesharp edge was broken by grinding to provide a inch root face. Theplates were placed upon a copper-faced steel platen (2 inches thick)with a distance therebetween of about inch. The plates were restrainedby clamping to the platen, two heavy duty C-clamps on either side beingused. Preheating was not employed and the temperature between passes wasmaintained below about 200 F. No postweld heat treatment was used.

sodium silicate and water as needed added to H ux in each instance.Ni-Si and From the data given in Table IV, it will be observed that inno instance was weld cracking observed. In those tests where pores weredetected, it can be said that the pores were extremely few and randomlydistributed. The degree of porosity was minimal at worst and wellwithin, for example, current military specifications which permit up to20 pores in a six-inch length in respect of /2 inch thick welds forcupronickels of the 70/30 type. Transverse slices taken from the weldedjoints confirmed the X-ray results and showed that the welds were freefrom objectionable defects. Slag was noted in the weld joint using fluxII, but this was expected since a core wire %2 inch in diameter was usedin the vertical position. This is too large as Well be appreciated bythose skilled in the art, a maximum core wire diameter of inch beingrecommended for vertical welding.

In addition to the foregoing, tensile tests were made in respect of theweld deposits formed using fluxes EE and QQ. The compositions of thedeposits and mechanical properties are given in Table V below:

10 introduce the silicon, titanium, (also chromium) in the form offerrous products, i.e., ferrosilicon and ferrotitanium. The chromium ispreferably added to the flux as electrolytic chromium powder. As toextrusion aids, others TABLE V Ni, Cr, Mn, Si, Ti, Y.S., U.T.S., EL,R.A., C.V.N., Flux percent percent percent percent percent K. s.i. K.s.i. percent percent it.-ll)s.

EE 30. 4 1. 5O 1. 74 0. 13 0.03 46 67. 6 18. 5 45 45 QQ 30.6 2.75 2.040.24 0.24 54.2 78.6 17 44.8 44

Norn.The balance of the compositions was virtually all Cu, the alloyscontaining not more than 0.05%

Ti, 0.03% Z1 and 0.75% Fe.

It will be noted the yield strength of the weld deposit formed usingflux EE did not reach 50,000 p.s.i., the flux containing but 7%chromium, whereas flux QQ, with 11% chromium, resulted in a yieldstrength well above 50,000 p.s.i. As indicated before herein, the fluxshould contain at least 9% chromium where yield strengths on the highside are desired. It should also be mentioned that the other mechanicalcharacteristics of the weld deposits were satisfactory.

In the light of all the foregoing, a particularly satisfactory fiuxcomposition which has consistently given excellent results contains 19%to 21% (20%) calcium carbonate, 19% to 21% (20%) cryolite, 19% to 21%(20%) manganese carbonate, 19% to 21% (20%) titania, about 9% to 11%chromium, about 0.8% to 1.2% (1.1%) silicon, about 1.1% to 1.4% (1.3%)titanium, and about 2% to 4% (3%) bentonite. To this should be added abinder, advantageously sodium silicate solution (say, 47 Baum) in anamount of 10% to (15%) by weight of the flux. This is recommended inproducing all electrodes.

In addition to joining a high strength chromium cupronickel to itself,as well as to chromium-free copper-nickel alloys of standardcomposition, notably the 70/30 type, flux covered electrodes of thepresent invention can also be used in joining wrought to castchromium-containing cupronickels. Core wires contemplated herein shouldbe of the same general composition as the chromium-free base platecomposition described hereinbefore.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. For example, since the silicon and titanium can beincorporated into the flux via nickel-silicon and nickel-titanium masteradditions, fluxes within the invention can contain up to about 8.85%nickel, although a smaller amount would be used when less than themaximum of these constituents were present. For example, approximately7.85% nickel would be found in the flux should 1.4% silicon and 1.5%titanium be present. It is preferred, however, not to which might beused, apart from bentonite, include alginates and mica. lSUChmodifications and variations are considered to be within the purview andscope of the invention and appended claims.

I claim:

1. A welding flux for welding copper-nickel base members containingabout 24% to 38% nickel, particularly when at least one of the memberscontains about 2.4% to about 3.8% chromium, said flux consistingessentially of about 10% to 40% calcium carbonate, about 5% to 40%cryolite, up to 30% manganese carbonate. about 10% to titania, from 7%to not more than 13% chromium, about 0.6% to about 1.7% silicon, about0.5% to 1.6 titanium, and up to 5% bentonite.

2. A welding flux in accordance with claim 1 containing 16% to 24%calcium carbonate, 16% to 24% cryolite, 16% to 24% manganese carbonate,16% to 24% titania, about 8% to 12% chromium, about 0.8% to l.4%silicon, and about 1% to 1.5% titanium.

3. A welding flux in accordance with claim 1 containing 19% to 21% eachof calcium carbonate, cryolite, manganese carbonate and titania, 9% to11% chromium, 0.8% to 1.2% silicon, 1.1% to 1.4% titanium and about 2%to 4% bentonite.

4. A welding flux in accordance with claim 1 containing up to about8.85% nickel.

5. A Welding flux in accordance with claim 2 containing 2% to 5%bentonite.

References Cited UNITED STATES PATENTS 2,745,771 5/1956 Pease et al.14823 3,107,176 10/1963 Witherell 117-205 3,125,470 3/1964 Witherell148-24 3,235,405 2/1966 Quaas 117205 L. DEWAYNE RUTLEDGE, PrimaryExaminer W. W. STALLARD, Assistant Examiner US. Cl. X.R.

